Wednesday, January 18, 2017

Atomic clocks down, new blow to Galileo – Challenges.fr

This is a new puzzle which Europe in space would have gone well. Jan Wörner, the director-general of the european space Agency (ESA), recognized Wednesday, January 18, a new technical issue on the Galileo satellites, the european alternative to the american GPS. On the 72 atomic clocks fitted to the 18 satellites already on-orbit, nine are down. “It’s a sensitive issue” because the atomic clocks are elements of a “very important” for the proper functioning of the system of navigation by satellite, said Jan Woerner during a press conference at the headquarters of ESA in Paris.

Concretely, each Galileo satellite is equipped with four atomic clocks : two “masers hydrogen passive”, in sabir technique, and two rubidium atomic clocks. These clocks are essential, because they allow the user to get his precise location. The receiver (smartphone, tool of GPS-type…) compares the time of emission and time of reception of the signal, and deduce the distance with the satellite. Just four satellites to obtain the location to the nearest metre, an accuracy allowed by the quality of the atomic clocks. They measure the time with an accuracy of about a nanosecond (a billionth of a second) per 24 hours. In other words, the margin of error is of a second… every 2.7 million years. In comparison, a quartz watch gains or loses about a second per day.

Precision record

Still it is necessary that the famous clocks work. With 9 clocks down on 72, that is 12.5% of the Galileo system, which is, in theory, out-of-service. Fortunately, each satellite has four clocks, it is necessary that the four are in HS so the satellite is not operational. “To this day, thanks to this redundancy of clocks, none of the satellites of the constellation is non-working,” said Jan Woerner.

prevents : such failures are the wrong kind, after the incredible succession of bugs and technical issues of program governance that is emblematic of european space. Between the delays in the ignition, a business plan poorly pinned (on the basis of a PPP) which explodes in mid-flight, multiple setbacks for industrial and technical, and two satellites in a bad orbit in 2014, the project, launched with great fanfare by the european Commission in 2001, shows a delay in… twelve years. The total cost of the program has also exploded : in an injunction issued last February, the Court of accounts the French was estimated at 13 billion euros, three times the initial budget of 4.6 billion. For France, the bill is expected to be 2.4 billion, thought the sages of the rue Cambon.

Threat on the next launch ?

The failure of the clocks falls even more evil than the european Commission, the programme’s manager, had formalized the launch of the first Galileo services last December 15. The urgency now is to identify the cause of breakdowns. The Galileo satellites are under control of the implementation of the German OHB, and the atomic clocks are being developed by the French group Orolia, in collaboration with Airbus Defence & Space and Selex Galileo. The problem is in any case deemed serious enough by the ESA to ensure that the issue of the postponement of the upcoming launches of Galileo to be asked. The next shot is expected in the third quarter of 2017 by an Ariane 5 in French Guiana, which should put into orbit four new satellites.